OTTAWA (Reuters) - A Canadian senator faced charges of assault and sexual assault on Friday after spending the night in jail, a new stain on the reputation of the upper house of Parliament, which the government wants to reform.

Police arrested Conservative Senator Patrick Brazeau, 38, on Thursday for alleged domestic violence, and on Friday he appeared in court to hear the charges against him.

He did not speak to reporters, and his office did not reply to several requests for comment.

Members of the Canadian Senate are appointed rather than elected, and they serve an uninterrupted term until they reach the age of 75. Critics say the institution is unaccountable, ineffective and in urgent need of change.

Prime Minister Stephen Harper, who appointed Brazeau to the Senate in 2008, kicked Brazeau out of the Conservative caucus on Thursday after he heard about the incident.

"Obviously the situation with Senator Brazeau is terrible. It is extremely appalling, disappointing. We all feel very let down," Harper said Friday in a televised news conference.

Brazeau will be released on bail with a court order to stay away from the alleged victim, who cannot be named due to a publication ban, said Crown prosecutor Sylvain Petitclerc. Brazeau's next court appearance is set for March 22.

The allegations against the senator came as he and two other members of the Senate come under scrutiny for what critics say are questionable expense claims. A Senate committee has asked auditors to study the expenses.

Harper has long pressed for changes to the Senate, perhaps by cutting the term of senators to eight years.

The government also wants senators to be elected rather than appointed, and last week it asked the Supreme Court to provide its opinion on its proposed changes, a process that could take up to two years.

The main opposition party, the New Democrats, wants to see the Senate abolished altogether.

Brazeau, an aboriginal leader from northern Quebec, was a controversial figure even before Harper chose him for the Senate.

Before being appointed, he headed an aboriginal organization. Since then, he has clashed with leaders of the native protest movement known as "Idle No More" and has made waves with frequent hostile exchanges on Twitter with reporters and critics.

A strapping, tattooed man with a background in martial arts, Brazeau famously lost a charity boxing match last year to Justin Trudeau, the celebrity son of former Prime Minister Pierre Trudeau and a candidate to lead the Liberal Party.